I have a 2012 Mazda6 with over 200k miles. It started making this chirping / squeaking noise while driving. But I noticed it takes a lil time before it starts after my car sits a while. So something had to warm up. Then I also noticed the sound when I switch the gear shift from reverse to drive or drive to reverse (automatic transmission). Also when I turn my air on or when the air is on and I'm sitting in traffic or at a red light I notice it. It's like any type of vibrations u can hear it. I have been to the Mazda dealership 3 times n they have replaced the exhaust gasket n made sure the heat shield was ok. But that didn't work. I have had my suspension replaced.  They have checked the engine mounts n belts. Still not fixed...I need help. No one seems to know why or exactly where the noise is coming from .